What test should be ordered to evaluate possible pulmonary hypertension in a patient with an intermediate probability of pulmonary hypertension, as suggested by a right ventricular systolic pressure (RVSP) of 37 mmHg?

Right Heart Catheterization is the Definitive Next Step

In a patient with RVSP of 37 mmHg, you should order right heart catheterization (RHC) to definitively evaluate for pulmonary hypertension, particularly if the patient is symptomatic or has additional echocardiographic signs of PH. 1, 2

Understanding the Echocardiographic Probability

An RVSP of 37 mmHg corresponds to an intermediate probability of pulmonary hypertension based on current ESC/ERS guidelines. 1, 2 Specifically:

• TRV 2.9-3.4 m/s (corresponding to PA systolic pressure 37-50 mmHg) places this patient in the "PH possible" category 2, 3
• This intermediate probability designation requires careful assessment of additional echocardiographic variables before determining next steps 1

Critical Additional Echocardiographic Signs to Assess

Before proceeding to RHC, you must evaluate for additional echocardiographic signs from at least two different categories: 1, 2

Category A (Ventricular signs):

• Right ventricle/left ventricle basal diameter ratio >1.0 1, 2
• Flattening of interventricular septum (LV eccentricity index >1.1) 1, 2

Category B (Pulmonary artery signs):

• RV outflow tract acceleration time <105 msec 1, 2
• Early diastolic pulmonary regurgitation velocity >2.2 m/sec 1, 2
• Pulmonary artery diameter >25 mm 1, 2

Category C (Right atrium/IVC signs):

• Inferior vena cava diameter >21 mm with decreased inspiratory collapse (<50% with sniff or <20% with quiet inspiration) 1, 2
• Right atrial area (end-systole) >18 cm² 1, 2

Decision Algorithm Based on Clinical Context

If the patient is symptomatic (dyspnea, fatigue, chest pain) AND has additional echocardiographic signs:

• Proceed directly to right heart catheterization 1, 2, 4
• RHC is mandatory before initiating any PAH-specific therapy 4

If the patient is symptomatic WITHOUT additional echocardiographic signs:

• Complete comprehensive PH workup first, then consider RHC based on findings 2, 4

If the patient is asymptomatic:

• Perform echocardiographic follow-up 2
• Consider alternative diagnoses 2

Comprehensive Workup Before or Concurrent with RHC

The following tests should be completed to identify underlying etiology: 4

• Complete blood count, comprehensive metabolic panel, liver function tests 4
• Thyroid function testing 4
• NT-proBNP for prognostic assessment 4
• HIV serology, antinuclear antibody (ANA), hepatitis serologies 4
• Ventilation/perfusion (V/Q) scan - preferred screening method for chronic thromboembolic pulmonary hypertension (CTEPH) due to higher sensitivity than CT angiography 4
• Pulmonary function tests with DLCO 1
• Six-minute walk test 2
• Sleep study evaluation (overnight oximetry or polysomnography) 1, 3

Why Right Heart Catheterization is Essential

Echocardiography alone is insufficient for treatment decisions. 1 The limitations are significant:

• Echocardiography may underestimate pulmonary artery pressure by a mean of 11 mmHg 4
• Underestimation of ≥20 mmHg occurs in up to 31% of patients 4
• The ±2SD limits of agreement between echo and catheterization are +19 to -18 mmHg for mean pulmonary artery pressure 5
• In severe tricuspid regurgitation, TRV may be significantly underestimated and cannot exclude PH 1

RHC provides definitive hemodynamic diagnosis: 4, 6

• Confirms PH (mean pulmonary artery pressure >20 mmHg) 6
• Distinguishes pre-capillary PH (PAWP ≤15 mmHg, PVR >2 Wood Units) from post-capillary PH (PAWP >15 mmHg) 6
• Guides treatment decisions and prognostication 4

Safety Profile of Right Heart Catheterization

When performed in experienced centers, RHC is safe: 7

• Overall serious adverse event rate: 1.1% 7
• Procedure-related mortality: 0.055% 7
• Most complications are mild to moderate (venous access issues, arrhythmias, vagal reactions) and resolve spontaneously or with intervention 7

Critical Pitfalls to Avoid

• Do not rely solely on RVSP or TRV for diagnosis - always consider the full clinical context and additional echocardiographic variables 2, 3
• Do not use exercise Doppler echocardiography for PH screening - this is a Class III recommendation due to lack of validated criteria 2, 3
• Do not initiate PAH-specific therapy based on echocardiography alone - RHC confirmation is mandatory 1, 4
• Do not assume a "low probability" echo excludes PH - patients can have PH even with normal echocardiograms, particularly if symptomatic with risk factors 2

Specialist Referral Timing

Immediate referral to a pulmonary hypertension center is warranted if: 4, 3

• High probability of severe pulmonary vascular disease on echo 6
• Signs of right heart failure are present 6
• RVSP ≥60 mmHg or TRV >3.4 m/s 4

Management requires expertise in hemodynamic assessment, vasoreactivity testing, and PAH-specific therapies. 4